Analysts often look for reputation of an IP or URL to categorize and act upon them when they are part of a suspicious communication. The below online sites will give reputation of URLs and IPs, provide their historical information and some of these sites will assess URLs in real time to identify threats.
Bitcoin is a virtual and unregulated digital currency, not issued by any central bank. It has no central authority and it can be exchanged like currency notes. It maintains anonymity. It's price is $11,182.50 as of June 25th 2019. Know more about bitcoins here
NFS(Network File System) is developed by Sun Microsystems for sharing files/folders between Unix systems. It allows to mount local file system on a network or a remote host to interact.